Method of extinguishing fires



United States Patent U.S. Cl. 2525 3 Claims ABSTRACT OF THE DISCLOSURE A fire extinguisher is provided which contains potassium aluminium fluoride as the extinguishant. To improve the flow of the extiuguishant, a lubricant such as a silicate can be added.

This invention relates to fire extinguishers containing dry powder extinguishants and to methods of extinguishing fires.

According to the present invention there is provided a fire extinguisher containing as the extinguishant potassium aluminum fluoride. A lubricant may be incorporated in the extinguishant.

The invention further provides a method of extinguishing fires comprising the step of covering burning material with a layer of potassium aluminium fluoride.

The invention further provides a fire extinguisher mounted in a location in which it will be exposed prior to use to temperatures in excess of 270 C., containing as the extinguishant potassium aluminium fluoride, preferably with an additive lubricant.

One advantageous property of potassium aluminium fluoride (which in its naturally occurring form is known as potassium cryolite) over conventional dry powder extinguishants, such as sodium bicarbonate, is that it can be exposed to relatively high ambient temperatures with out decomposition. Thus one particular use of fire extinguishers containing extinguishant in accordance with the invention is in applications where the extinguishant wlil be exposed prior to use to ambient temperature in excess of 270 C., for example of the order of 300 C.

Unlike sodium bicarbonate and some other conventional extinguishants, potassium aluminium fluoride is not deliquescent and does not therefore require protection against moisture to prevent caking, such as by a waterproof coating of the particles. However, where it is found desirable to improve the flow of the powder an additive lubricant may be used. Example of suitable lubricants for this purpose are silicates, such as precipitated calcium silicate or aluminium silicate, precipitated silica and micronised silica gel. Such lubricants can be used at the high ambient temperatures referred to above. It will be appreciated that the amount of lubricant added will de- 3,544,459 Patented Dec. 1, 1970 pend upon the configuration through which the powder is to be discharged, the proportion of lubricant being high where the minimum cross-sectional area through which the extinguishant must pass is small and being progressively reduced for extinguishers where this minimum cross-sectional area is greater. Thus, whilst the percentage of additive will normally be about 1.0% to 2.0% by weight it may be found that as little as 0.5% will give useful lubrication where there are no small cross-sectional areas in the discharge passage, whilst as much as 5.0% may be required where there are relatively small cross-sectional areas in the discharge passage.

The invention is particularly applicable to remotely operated extinguishers used in aircraft which are liable to be subjected to high ambient temperature, particularly in aircraft engines. A typical extinguisher of this kind from which the extinguishaut of the present invention could be discharged is disclosed in U.S. Pat. N0. 3,209,937 of R. Hurst et a1. issued Oct. 5, 1965. However, the invention is also applicable to hand-held and other types of fire extinguishers. A typical hand-held extinguisher from which the extinguishant of the present invention could be discharged is disclosed in U.S. Pat. No. 3,233,783 of M. J. Thornton issued Feb. 8, 1966.

The extinguishant is applied to burning material to extinguish it in the manner normal with powder extinguishants.

What I claim is:

1. A method of extinguishing a fire comprising the step of applying potassium aluminium fluoride to burning material.

2. The method of claim 1 in which the potassium aluminium fluoride is expelled from a container.

3. The method of claim 1 in which the potassium aluminimum fluoride is mixed with a lubricant selected from the group consisting of precipitated calcium silicate, precipitated aluminium silicate, precipitated silica and micronized silica gel.

References Cited UNITED STATES PATENTS 3,080,316 3/1963 Petertyl et al 2522 3,179,588 4/1965 Siimes 2525X 3,267,030 8/1966 Dessart 2527 OTHER REFERENCES Rose et al.: Condensed Chemical Dict., 1961, Reinhold Pub. Co., New York, N.Y., p. 25.

MAYER WEINBLATT, Primary Examiner U.S. Cl. X.R. 2522 

